The gene schmalspur functions in mesoderm formation in zebrafish, and interacts with notail and spadetail

The gene schmalspur is involved in the Nodal signalling pathway to maintain the expression of nodal genes during zebrafish development. Mutants for no dal-related genes show a partial loss of axial mesoderm, which is also defe ctive in embryos lacking maternal and zigotic expression of schmalspur. We have generated double mutants of schmalspur with other genes responsible fo r mesoderm formation and have analyzed the phenotype and the genetic intera ctions by whole-mount in situ hybridization. In addition, cellular transpla nt experiments were carried out to determine how schmalspur functions in me soderm formation. Our results show a close genetic interaction of schmalspu r with the T-box genes notail and spadetail, since the axial and paraxial m esoderm of these double mutants were strongly affected, and a non-cell auto nomous function for schmalspur in mesoderm formation.